DynaSand^® Deni is a low energy, low maintenance vertical sand filtration plant for nitrogen removal from the final discharge using the extensively proven DynaSand^® Deni process.

DynaSand^® Deni denitrification helps reduce the adverse environmental impact of excess nitrogen compounds from treatment works into receiving watercourses.

Incoming water flows upwards through the DynaSand^® Deni filter bed, where nitrite (NO2) and nitrate (NO3) are converted into gaseous nitrogen (N2) by microbial action. Nitrogen is discharged to the atmosphere by the airlift pump as a continuous stream. The vertical configuration of the DynaSand^® Deni means a 90% smaller footprint than the equivalent horizontal sand filtration beds.

• Continuous process with the addition of nitrate removal.
• Nitrate, suspended solids and BOD removal in a single stage.
• Space saving.
• The N₂ generated is simply removed by the air-lift pump, thus no "bed bumping" is needed.
• Predators cannot survive the action of the air-lift pump and sand washer.
• Offers scope for automatically controlled addition of carbon, which prevents an increase in BOD caused by over-dosing.
• Stand alone addition to the works.

The DynaSand^® Deni filter, like the DynaSand^® filter, is based on the counter flow principle.  To provide optimum conditions for the detnitrifying bacteria, a carbon source such as methanol is added to the wastewater stream prior to the filter.  The water to be treated (red arrow) is admitted through the inlet distributor (1) in the lower section of the unit and is cleaned as it flows upwards through the media bed, prior to discharge (blue arrow) through the filtrate outlet (2) at the top.  The carbon source encourages the growth of heterophic denitrifying bacteria within the filter media bed.

The media containing the entrapped solids is conveyed from the tapered bottom section of the unit (3), by means of an airlift pump (4), to the media washer (5) at the top. 

Cleaning of the media commences in the pump itself where impurities are separated from the media grains by the turbulent mixing action.  The contaminated media spills from the pump outlet into the washer labyrinth (6) in which it is washed by a small counter current flow of clean water.  The separated solids and sloughed biomass (brown arrow) are discharged through the wash water outlet (7), while the grains of clean media (which are heavier) are returned to the media bed (8).  As a result, the bed is in slow, constant downward motion through the unit.  Compressed air for the air lift pump is provided via the air distribution panel.

Thus, water purification and media washing both take place continuously enabling the filter to remain in service without interruption.

Frequently Asked Questions

Q. What is the difference between a DynaSand^® and a DynaSand^® Deni?

The internals of the filters are identical; DynaSand^® Deni filters can be taller, as media volume dictates treatment capacity. The most important difference is that DynaSand^® Deni filters require chemical dosing of a carbon source for the denitrification process.

Q. Can I use sludge return liquors instead of methanol as a carbon source?

It is possible to use return liquors, but these liquors tend to vary in concentration, and therefore can be unreliable when dosed, causing either too much carbon to be applied leading to BOD failures or too little leading to nitrate failures.